Factors that cause Vasodilation
Increase in CO2, extracellular K+
Decrease in O2, pH
Epinephrine: only when acting on Beta-2 receptors: results in relaxation of smooth muscle (arterioles in skeletal muscles)
-potent vasodilator synthesized when the [K+]
-NO as a gas will diffuse from one cell to another and act locally to cause vasodilation
-involved in variety of responses to stimuli and trauma
-Released by mast cells in excessive response to allergies
-increased blood flow, increased capillary permeability to cause swelling
-Released with high metabolism and decrease in O2
-Important in heart skeletal muscles and liver
-Increase blood flow so that when there is lot of activity, adenosine is released and there will be vasodilation and increase in blood flow
NE's effect on vasoconstriction
E's effect on vasoconstriction
NE acts on Alpha-1 receptors
E acts on Alpha-1 or B-2 to either constrict or dilate depending
Causes vasoconstriction; released by endothelin cells locally
Angiotesin II hormone
-all arteries have receptors for angiotesin so it will increase in vasoconstriction in all vessels
-many treatments for hypertension either block production of angiotensin II or block the receptors for angiotensin II
How is vasoconstriction tonically controlled?
Autonomic system has tonic control so that there is a certain frequency of APs that release a certain amount of E and have a certain degree of vasoconstriction via Alpha-1 receptors
How does E activate Beta-2 receptors rather than Alpha-1 receptors?
by having a higher concentration of E than NE
What is the main point of Circulation?
Capillary Exchange (or gases and h2o)
Simple Diffusion in Capillaries
only gases (O2, CO2) since they are soluble across the bilayer and can diffuse
Bulk Flow in Capillaries
way by which H20 and small molecules can diffuse across the capilaries into tissues
-pores aren't large eoungh to allow proteins in plasma across
What forces regulate Bulk Flow
1. Hydrostatic Pressure
2. Osmotic Pressure
equals difference between hydrostatic pressure in capillaries and the hydrostatic pressure in the interstitial fluid
Is the hydrostatic pressure usually higher int he capillaries or in the interstitial fluid?
Hydrostatic pressure is usually higher in the capillaries than in the interstitial fluid
H20 flow is usually outward due to hydrostatic pressure
(aka Colloid Pressure)
contributed by impermeable solutes (plasma proteins)
Since only found in plasma, this only flows into capillaries and out of the interstitial fluid
What is the main contributor of plasma proteins to osmotic pressure?
Net flow equation for Fluid exchange in capillaries
Net Flow=K(Pcapillary-Pinterstitial fluid)-(Πcapillary-Πinterstial fluid)
Where P= Hydrostatic Pressure
Where Π= Osmotic Pressure
When hydrostatic pressure drops along the capillaries so that osmotic pressure increases and there is a net absorption at the end of a capillary bed but net filtration at the beginning of the capillary, what does this cause?
Net loss of fluid into interstitial fluid and this is picked up by the lymphatic system
Does hydrostatic pressure increase or decrease due to vasodilation?
what does this do to filtration? what does this then do to the interstitial water?
increase filtration=> excess water in H2O in interstitial which leads to edema
-occurs in high altitudes
How could you move water from the interstitial area into the capillaries and then into the kidneys to be urinated out
by wrapping yourself in tight bandages in order to increase hydrostatic pressure so that water will diffuse into the capillaries and into the kidney then out for urination
-picks up excess fluid that is not taken up in the capillaries
-excess fluid enters lymph vessels which eventually return this fluid to the circulation
Metastasis in Cancer
can spread by
1. entering the blood
2. entering lymphatic system
parasites that plug up the lypathics. Results in swelling of the legs, arms and scroumex